* If Louis' clothing change from a sweater and combat gear to a [[Film/ShaunOfTheDead white dress shirt and a red tie]] doesn't clue you in...
* The Passing has a bunch of graffiti:
-->"[[DeadRising Otis: Out of film. No helicopters. Zombies too fast. Not going to make it. --Frank West]]"
-->"[[Film/DawnOfTheDead Roger, went to the mall --Francine]]"[[note]]The 1978 version.[[/note]]
-->"[[Film/DawnOfTheDead2004 Went to save my dog. If not back in 15 minutes, everyone drop everything and come save me. --Nicole]]"[[note]]The 2004 version.[[/note]]
-->"Looking for an M60? Come see me. --[[VideoGame/PlantsVsZombies Crazy Dave]]"
-->"[[Film/TwentyEightDaysLater REPENT. THE END IS EXTREMELY FUCKING NIGH.]]"
-->"[[Film/ShaunOfTheDead Ed is King of the Zombies]]"
* The arena in the finale of Dark Carnival is conveniently named The Peach-Pit. This may in fact be a reference to the diner in ''BeverlyHills90210'', in which the diner hangout was named the same. Or to a certain {{Mangaka}} who goes by that as their pseudonym, which too is based on the same show.
* Some of the graffiti (and one of the achievements) in the first game references the "Zombie Genocider" achievement of ''DeadRising'' which rewarded the player for killing 53,594 zombies. ''Left 4 Dead'' tops it by exactly one zombie.
** It appears that this has caught on; ''VideoGame/{{Prototype}}'' has a "Trail of Corpses" achievements, for killing 54,596 infected. Difference being that the ''Prototype'' Infected are totally not zombies.
** Valve introduced a new twist -- the "Littlest Genocide" achievement, which requires you to kill 5,359 zombies on the Crash Course DLC campaign.
* The first game takes place in Pennsylvania, starting in Philadelphia and moving outwards from there. George Romero's movies were all set in Pennsylvania.
* One of Zoey's numerous film references:
-->"Oh, nice, [[Franchise/EvilDead a cabin in the middle of nowhere]]. [[KillEmAll I know how this movie ends]]."
* There are countless shout outs to zombie movies ranging from things Zoey says to a room where you can see the remains of a zombie killed by a lawn mower.
* The messy [[ChainsawGood lawnmower]] scene in Blood Harvest is a shout out to the zombie movie ''Film/{{Braindead}}'', which was directed by Peter Jackson.
* The campaigns themselves are a homage to the entire zombie movie genre. Each campaign is presented as a movie, with a theatrical poster at the beginning and a credits sequence at the end. All in-game graphics are shown under a subtle film grain filter, and musical cues are used to highlight certain situations. Various zombie movie tropes are played with. And of course, the placement of enemies and items being controlled by an AI ''Director''.
* A brilliant reference to a completely non-zombie movie:
-->"[[Film/{{Ghostbusters}} He slimed me!]]"
* Even though it's ostensibly from a fictitious school, Louisiana gamers may appreciate that Coach wears [[http://en.wikipedia.org/wiki/LSU_Tigers a purple and gold shirt]].
** Fun Fact: Purple, gold and green are [[http://www.mardigrasneworleans.com/mgcolors.html the official colors of Mardi gras]] and LSU adopted the first two while rival Tulane took green.
* The Dead Air campaign features a shout out to Nietzsche. [[NietzscheWannabe A man spray-painted "God Is Dead"]] (a phrase made famous by Nietzsche himself) on the walls at several points before he apparently killed himself.
--> '''Zoey:''' "Oh no, the Zombies killed God!"
--> '''Francis:''' "God's dead, huh? Well, join the damn club."
* Upon picking up an SMG, Louis might say, "This is just like in ''VideoGame/{{Counter-Strike}}''!". Which itself is a reference to how ''Left 4 Dead'' started when the dev team of ''VideoGame/CounterStrike: Source'' was messing around with playing as armed Counter-Terrorists against knife wielding Terrorist bots.
** Louis has an unused line in Left 4 Dead 2 for picking up a Crowbar. "Man, I feel like [[VideoGame/HalfLife Gordon Freeman!]]"
** One of Ellis' community campaign stock lines, "Dude, this is just like ''VideoGame/TeamFortress2''!"
* During Dark Carnival, you may notice "Pyro's Hamburgers" and "Heavy Gulp" signs on some of the stands.
* "[[Film/{{Aliens}} Game over, man! Game over!]]"
* The escape vehicles in ''Crash Course'' are clearly modeled on the zombie-smashing buses from the ''Film/DawnOfTheDead2004'' remake.
* Sometimes when Zoey picks up a shotgun, she will say "[[Franchise/EvilDead Groovy.]]"
** Usually triggered right after Francis does; he has a similar line:
---> '''Francis:''' Groovy! ''(either Louis or Zoey snickers audibly)'' What? It ''is'' groovy!
* One scene in the trailer for Left 4 Dead 2 shows Coach eating a chocolate bar and another scene has Nick make fun of Coach by trying to convince him to go up the stairs faster saying that the escape helicopter is made out of chocolate. This could be a possible reference to [[PunchOut Doc Louis]] who also had a heavy preference to chocolate.
** Note that the chocolate bar Coach is eating was a "chocolate helicopter." Just look on the box by Rochelle which says "choco Heli" and mentions something about blades.
* In the first map of The Parish, a jukebox can be played in the bar and has a few songs selected at random, one of them being ''[[VideoGame/{{Portal}} Still Alive]]''.
** And by [[JonathanCoulton the same singer]], "Re: Your Brains."
* "Dark Carnival" may be a shout out to ''HouseOfTheDead: OVERKILL'''s "Carny" level, or possibly the "Dark Carnival" level from ''VideoGame/{{Blood}}'' (a game brimming with shout outs). Or, for that matter, any of a dozen horror movies that have used [[CircusOfFear circuses and theme parks]] as settings or set pieces.
* The gnome you win for getting 750 points at the shooting range game is ''the exact same model'' as the gnome from ''VideoGame/HalfLife2: Episode 2''.
** And, just like its predecessor, you get an achievement for carrying it with you for the whole campaign.
** Its name, "Gnome Chompsky", references the noted linguist and psychologist [[http://en.wikipedia.org/wiki/Noam_Chomsky Noam Chomsky]].
* "Swamp Fever" begins the same way "Crash Course" does: one Survivor having shot the infected pilot, and another berating him for it.
* [[Film/TheBluesBrothers "Disco pants and haircuts. Man, lots of space in this mall."]]
* The female soldier seen [[http://www.l4d.com/comic/comic.php?page=76 here]] in Part 2 of the Sacrifice comic may be a shout out to [[VideoGame/TeamFortress2 The Pyro]] as the two share the same distinctive gasmask and suffer from a bit of gender confusion.
* Louis has a figure of [[VideoGame/TeamFortress2 Heavy Weapons Guy]] on his desk in Part 1 of the Sacrifice comic.
* Part 3 of the Sacrifice comic has a poster of [[VideoGame/DeadRising2 Chuck Greene]] found in this [[http://www.l4d.com/comic/comic.php?page=101 page]]. It also has a hidden image of Ellis wearing Chuck's default ''Case Zero'' shirt with the text of "The Left 4 Dead 2 team congratulates the Dead Rising 2 team on their release".
* During "The Sacrifice", Francis points out that they have no evidence that Louis is not crazy. Louis responds that he would [[Literature/TheSilenceOfTheLambs love to make a lady suit out of Francis, and Zoey says she hates putting the lotion in the basket]].
* The achievement for killing a Special Infected with an {{Exploding Barrel|s}} is called [[VideoGame/StarFox64 Barrel Rolled]].
* The achievement you get at the end of The Sacrifice if you have Bill sacrifice himself is aptly named Film/KillBill.
* When coming upon the trapped Tank in The Sacrifice, Louis may quip "[[Film/SnakesOnAPlane tanks on a train]]".
* At the end of The Passing, Zoey may quote the "you blew it up" speech from Franchise/PlanetOfTheApes.
* Nick sometimes calls himself [[WesternAnimation/TheSimpsons "Dr. Nick"]] when healing a teammate.
* In line with her profession as a producer in the news, Rochelle is heard to say [[Film/AnchormanTheLegendOfRonBurgundy "Knights of Columbus!" and "Son of a bee-sting!"]] when hurt.
* At one point in the Crash Course campaign, the survivors must pass through a small area with a broken steam pipe. Francis says "watch out for that steam pipe!", quickly followed by veiled references to a different kind of {{Steam}}.
--> '''Zoey:''' Man, I love steam.\\
'''Francis:''' Oh yeah, I love steam. [[SelfDeprecation I just hate the pipes.]]
* When Ellis picks up an axe, there's a chance of him saying [[Film/TheShining "Heeeeere's Ellis!"]]
* Or if he grabs a chainsaw, [[Film/ArmyOfDarkness/Man, if I lose my hand, I'm stitchin' this thing onto the stump."]]
* Something of an EasterEgg, there's a very small chance that, upon getting hit with friendly fire, Nick will say
[[Series/ArrestedDevelopment "You're going to shoot the guy in the 3000$ suit? COME ON!]]
----